Soaking pit firing control



Nov. 4, 1941.

G. R. MCDERMOTT 'SOAKING PIT- FIRING CONTROL f Filed oct. 22, 1940 Srwentor (Ittomeg Patented Nov. 4, 1941 SOAKING PIT FIBING CONTROL Ottawa Hills, IOhio, as'

George B.. McDermott,

signor to Surface Combustion Corporation, yToledo, Ohio, a corporation of New York Application October 22, 1940, Serial No. 362,220

1 Claim. l (Cl. 263-43) The heating of steel ingots to a temperature necessary for forging or rolling is usually accomplished by standing the ingots on end in a directred pit which has a waste\gas port in connection with a source of draft such as a stack, there usually being a battery of such pits all s'erved by one stack. Inasmuch as the pits are independently red, some may be on high ring rates andfothers on low rates. The same stack draft on all of the pits is therefore not conductive to proper heat distribution in a pit which is being tired at a rate dierent from the other pits. Attempts have been l made to overcome this diiiiculty by providing a waste gas damper for each pit, the position of the damper being controlled by the waste gas pressure prevailing between the pit and damper. 'I 'his arrangement, however, has not proven entirely satisfactory particularly on low ring rates and it is therefore the object of the present invention4 to provide an improved arrangement for controlling the heat distribution in the pit.

In accordance with the present invention, each pit is provided with a waste gas damper but instead of controlling the position of this damper as above mentioned its position is controlled by means responsive to a change inthe rateA of fuel supply to the pit. This manner 'of controllingthe position of the damper gives superior name distribution in the pit and especially in a pit where the iiame travels in a more or less U-shape path between the ring port and the exhaust port.

'I'he preferred mechanism for controlling the position of the pit damper in accordance with the present invention can best be explained in connection with the accompanying drawing wherein the single figure is a more or less diagrammatic representation of a soaking pit furnace with the present invention applied thereto.

In the drawing,`9 indicates a pit wherein ingots I (shown in broken lines) ,are adapted to be. placed in upright position on the iloor or hearth Il ofthe pit. The pit has lthe usual cover I2 adapted to be moved to one side for the insertion A and removal of the ingots. i3 indicates the ring port for the pit and Il the waste gas outlet port. The ame in travelling from the burner port to the exhaust port normally tends to iiow in a more or less Uv-shape path as indicated by the arrows. A flue I5 leads from the outlet Il to a waste gas manifold I6 which delit'ers to a stack I'I by way of a connecting flue passage I8.` It will be understood that the manifold IIS is common to a battery of pits 9.

Y A stack damper is indicated at I 9, the same upper end is secured to an operating device 2l for raising and lowering the damper, this device being connected by a tube 22 to the manifold I6, whereby draft pressure in the manifold is effective-on the ,operating device 2l, it being understood that the de'vice 2| will operate the damper I9 in a manner to maintain a substantially constant`draft pressure in the manifold I6. This arrangement eliminates variations in stack draft' and represents nothing novel.

-Fuel and combustion-supporting air are delivered to the iiring port by conduits 50 and M leading from pressure supply mains 52 and 46 reof fuel and combustion-supporting air supplied to the furnace, and in the drawing I have shown a well known means for that purposev and have also shown how a movable element of said means may be utilized to control the position of the damper 23 to attain the object of the present invention. a

In the proportioning system shown there is a metering orice 5I in the gas supply conduit and a similar oriiice in the air supply conduit. the latter also being provided with a throttle valve 54 whose position is controlled by-means responsive to a relative change in iiow in the two conduits 4I and 5I). If, for exampleythe gas valve .53 is adjusted to increase or decrease the supply of fuel to the furnace, the control means would automatically adjust the position Yof the throttle valve 54 to make corresponding adjustment in the air supply in order to maintain the fuel-air ratio constant. The control means comprises two diaphragme 36 and 31 each in its own case 38 and 39 respectively,the diaphragms being interconnected by a tie rod '35 so that they must move as a unit. Pipes III and 4I lead from the opposite sides of the metering orice l5 to opposite sides of the diaphragm 38 and pipes 48 and I9 lead from opposite sides ofthe metering oriiice 5I to opposite sides of the diaphragm 31. If there is any relative change in now in the two conduits being shown as suspended by-a cable 20 whose 55 44 and 5I! the diaphragms will move towards the right or left as the case may be aswill be readily understood. The throttle valve 54 is connected by suitable linkage to a piston 2U in a cylinder 21, the said linkage being shown as comprising the piston rod 29, a cross head 2l and a cable 55. Operating fluid is delivered to one end or the other of the cylinder by pipes 30 and 3| leading from a housingv32 which serves to support the diaphragm cases 38 and 3 9. Operating fluid is supplied to one or the other of the pipes 3l and 3l by a pressure noz'zle connected to the tie rod 35 for movement therewith. Fluid under pressure is supplied to the nozzle by a supply pipe 34. It will be understood that when the nozzle 33 is midway betweenthe inlets ofthe pipes 30 and 3l the piston 23 will notbe moved.

In view of the fact that the gas-air'ratio control systemabove described embodies a metering orifice 5I in the fuel supply conduit and embodies a movable element in the form of piston 26 f or adjusting the position of the throttle valve 5I to compensate for a change in flow through the fuel supplyconduit. I have found it convenient and practical toemploy the piston 2l for adjusting the positionof the damper 23 to attain the object of the present invention. As I show, the operating'connection between the damper and the piston may consist of a cable 2l leading from the crosshead 23 and over a pulley 25 to the damper. The invention, however, is not limited to the use of the particular gas-air ratio control system disclosed. The important thing is the use of means responsive 'to a change in the amount of fuel supplied to the furnace for adjusting the position of the damper 23, for the purpose described.

The orifices I5 and 5I in the air and fuel lines respectively cause a differential pressure to be established in the lines, i. e., there will be a relatively high pressure on the intake side of the orifices and a relatively low pressure on the discharge side of orifices. The lines lll, 4I, and 4I, 43 are taken from the fuel and air lines in those high and lowpressure zones and impose them on the diaphragms 33 and 31 which in turn control the motion of motor 21 and ultimately the position of damper 23 and throttle Il. It is apparent therefore that a change in the rate of ow f in either of lines and will cause a variation in the pressure differential at the several orices. While the disclosurel shows a differential in both lines the control of damper 23 may bedetermined by a diilerential pressure in either line.

What I claim is:

A soaking pit comprising in combination, a chamber wherein ingots are placed for heating by a flame in said chamber, means including a metering orifice for supplying fuel to said chamber to produce said iiame, an exhaust passage leading from said chamber, a damper in said passage, means responsive to a change in differential pressure at said orifice for adjusting said damper to vary the effective discharge area of said passage, a waste gas manifold to which said passage delivers, and means for maintaining a substantially constant gas pressure in said manifold.

GEORGE R. McDERMO'I'I. 

